1. Field of the Invention
The present invention relates generally to automated machine control and, in particular, to an agricultural spray boom height control system and method.
2. Description of the Related Art
Movable machinery, such as agricultural equipment, open-pit mining machines, airplane crop dusters, and the like all benefit from accurate global navigation satellite system (GNSS) high precision survey products, and others. However, in existing satellite positioning systems (SATPS) for guided parallel and contour swathing for precision farming, mining, and the like, the actual curvature of terrain may not be taken into account. This results in a less than precise production because of the less than precise parallel or contour swathing. Indeed, in order to provide swaths through a field (in farming, for example), the guidance system collects positions of the vehicle as it moves across the field. When the vehicle commences the next pass through the field, the guidance system offsets the collected positions for the previous pass by the width of the equipment (i.e. swath width). The next set of swath positions is used to provide guidance to the operator as he or she drives the vehicle through the field. The current vehicle location, as compared to the desired swath location, is provided to the vehicle's operator or to a vehicle's steering system. The SATPS provides the 3-D location of signal reception (for instance, the 3-D location of the antenna).
Various navigation systems for ground-based vehicles have been employed but each includes particular disadvantages. Systems using Doppler radar will encounter errors with the radar and latency. Similarly, gyroscopes, which may provide heading, roll, or pitch measurements, may be deployed as part of an inertial navigation package, but tend to encounter drift errors and biases and still require some external attitude measurements for gyroscope initialization and drift compensation. Gyroscopes have good short-term characteristics but undesirable long-term characteristics, especially those gyroscopes of lower cost such as those based on a vibrating resonator. Similarly, inertial systems employing gyroscopes and accelerometers have good short-term characteristics but also suffer from drift. Various systems include navigating utilizing GNSS; however, these systems also exhibit disadvantages. Existing GNSS position computations may include lag times, which may be especially troublesome when, for example, GNSS velocity is used to derive vehicle heading. As a result, the position (or heading) solution provided by a GNSS receiver tells a user where the vehicle was a moment ago, but not in real time. Existing GNSS systems do not provide high quality heading information at slower vehicle speeds. Therefore, what is needed is a low cost sensor system to facilitate vehicle swath navigation that makes use of the desirable behavior of both GNSS and inertial units while eliminating or reducing non-desirable behavior. Specifically, what is needed is a means to employ low-cost gyroscopes (e.g., micro electromechanical (MEM) gyroscopes) which exhibit very good short-term low noise and high accuracy while removing their inherent long-term drift.
Providing multiple antennas on a vehicle can provide additional benefits by determining an attitude of the vehicle from the GNSS ranging signals received by its antennas, which are constrained on the vehicle at a predetermined spacing. For example, high dynamic roll compensation signals can be output directly to the vehicle steering using GNSS-derived attitude information. Components such as gyroscopes and accelerometers can be eliminated using such techniques. Real-time kinematic (RTK) navigation can be accomplished using relatively economical single frequency L1-only receivers with inputs from at least two antennas mounted in fixed relation on a rover vehicle. Still further, moving baselines can be provided for positioning solutions involving tractors and implements and multi-vehicle GNSS control can be provided.
Providing additional antennas in combination with standard SATPS and GNSS guidance, as mentioned above, along with optional gyroscopes is an effective method to increase GNSS positioning precision and accuracy, such as is described in U.S. Patent Publication No. 2009/0164067, which is assigned to a common assignee and is incorporated herein. However, accuracy and precision can only improve the efficiency of working vehicles, such as those in the agricultural field, to a limited extent. Although such systems are able to track and guide vehicles in three dimensions, including along ridges and sloped-regions, errors may appear in other aspects of a working vehicle. For example, in an agricultural field-working situation where a tractor is towing an implement, the implement may slide on a sloped-region, or the tractor may list to one side or another when entering softer soil or rocky areas. This can happen repeatedly when a vehicle is guided around the same field, regardless of the precision of the guidance system in pre-planning a path. Thus, a system that can detect such changes in uniformity of a field as the vehicle traverses a path and remember those changes can predict and re-route a more accurate and more economical path than a guidance system alone. Heretofore there has not been available a system and method with the advantages and features of the present invention.
Conventional agricultural spraying operations are carried out over an entire field, everywhere the crop is planted. In contrast, environmental spraying allows the spraying of certain materials which require restrictions in the area of deposition due to potential toxicity or strength. The restrictions can include the distance from waterways and slope of the ground which can affect run-off and concentrations of deposits.